Palynostratigraphy and paleoenvironments of the upper Turonian–lower Campanian Abderaz Formation in the east of Kopet-Dagh Basin (NE Iran)

Abstract

The palynology and palynofacies of the Abderaz Formation have been studied to interpret the paleoenvironments and sea-level changes in the Upper Cretaceous deposits of the Kopet-Dagh Basin. This formation in the Kalat-e-Naderi region (Gharesu section) is composed of 462 m of gray to cream shales, marlstone layers and three chalky limestone units. Seven dinoflagellate cyst (dinocysts) and four planktonic foraminiferal biozones have been identified in the studied succession, which suggest a late Turonian–early Campanian age for this interval. Four different depositional environments have been recognized in the studied section based on the relative proportion of organic matter (terrestrial organic matter, marine palynomorphs and amorphous organic matter). High abundance of marine palynomorphs in most samples indicates the predominance of an oxygenated distal shelf environment in the upper Turonian–lower Campanian interval. Seven third-order depositional sequences are proposed for the Abderaz Formation. A good correlation of sequence boundaries with the global sea-level fall events suggests that eustasy played an important role during the deposition of the Abderaz Formation.